Exam 3 Short Answers

Question 0

There are various chemicals in the environment that can negatively impact the conduction of action potentials form motor neurons  muscle fibers. Give one example of a chemical that blocks the gated ion channels from opening, its mechanism of action (how it works), and possible effects. Conversely, give one example of a chemical that leaves gated ion channels open too long, its mechanism of action, and possible effects.

Answer 0

Curare:

• blocks ion gated channels from opening
• kills & blocks receptor sites

Sarin gas:

• leaves ion gated channels open too long; muscles keep contracting & ATP runs out
• organophosphorus compound, cholinesterase inhibitor

Question 1

The coroner was unable to remove the small container of sleeping pills from the clenched hand of a suicide victim. Explain the reason for this.

Answer 1

• after death muscles undergo rigor mortis, development of rigid muscles
• ATP production stops
• ATP is no longer available to bind to myosin molecules
• cross bridges are unable to produce contractions

Question 2

Briefly but concisely give the steps involved in smooth muscle contraction and relaxation.

Answer 2

• Calcium ions diffuse through Ca2+ channels
• combines with calmodulin & binds with myosin kinase which causes contractions & activates
• relaxation occurs when myosin phosphate removes phosphate from myosin

Question 3

Propose a way in which Botulism could cause death

Answer 3

• botulism toxins block nerve functions
• lead to respiratory & muscular paralysis
• toxin causes death due to respiratory failure